Over the years, medical catheters have been developed and refined to provide useful devices for the diagnosis and treatment of disease without invasive surgery. As a result, medical catheters are widely used for a variety of modern, less invasive medical procedures. Unfortunately, the vast majority of catheters available today are manufactured and packaged as disposable, single use devices. While these conventional catheters are undeniably beneficial in shortening hospital stays and in reducing complications associated with surgery, the precision and quality control required to fabricate these instruments makes them expensive to produce and use. This is particularly true for disposable catheters. Moreover, the use of disposable catheters tends to increase: the amount of medical and packaging waste generated while eliminating the ability of the user to adapt the configuration of the catheter to specific needs and operating conditions.
These and other limitations associated with the use of disposable catheters are particularly well illustrated by catheters used for the treatment of vascular diseases. Over the last decade a medical procedure known as angioplasty has become widely accepted as a safe and effective method for opening stenoses throughout the vascular system and particularly for opening stenoses in the coronary arteries. The most common form of angioplasty practiced to date is known as percutaneous transluminal coronary angioplasty (PTCA).
In virtually all forms of PTCA, a long, hollow dilatation catheter having an inflatable balloon at its distal end is guided into a patient's artery and, using a fluoroscope and radiopaque markers for visualization, maneuvered within the artery until the balloon is positioned across the narrowing stenosis responsible for inadequate blood flow to the heart. Generally, a thin guide wire is first advanced into position and used to maneuver and direct the catheter. Once positioned, the balloon is inflated for a brief period by supplying pressurized fluid to the balloon through an inflation lumen in the catheter body, to displace the plaque or other obstructions causing narrowing in the artery. Applying negative pressure to the inflation lumen collapses the balloon allowing the catheter to be withdrawn when the stenosis has been opened and blood is once again flowing adequately. Thus, in contrast to the serious risks and complications previously associated with open-heart surgery, PTCA can be utilized to open blocked coronary arteries using only a small vascular incision through which the dilatation catheter is inserted and operated.
Several different types of entirely disposable dilatation catheters are currently in use and may be generally classified based upon their interaction with the guide wire. One common dilatation catheter design is known as the "fixed-wire" or integrated "balloon-on-a-wire" dilatation catheter. These single-lumen catheters utilize a relatively small diameter guide wire positioned within the inflation lumen and fixed to the distal end of the dilatation balloon. This design produces a very small diameter or "low-profile" assembly which is able to cross severely narrowed lesions and to navigate tortuous vascular pathways. More recent balloon-on-a-wire designs allow the catheter to be removed while leaving the guide wire in place across the stenosis.
Another common type of dilatation catheter design is known as the "over-the-wire" balloon catheter. This device typically utilizes a relatively large lumen for passage of a removable guide wire and for injection of angiographic visualization dye to assist in the placement of the distal expansible balloon across a target lesion. A second, parallel lumen is provided for inflation and deflation of the balloon with such a design commonly referred to as a "dual lumen" catheter. Alternatively, a "coaxial" design may be utilized where the catheter body defines an annular inflation lumen around the internal guide wire lumen.
More recently, "rapid exchange" catheters have been developed to allow for the quick removal and replacement of the catheter from the patient while leaving the guide wire in place for rapid reaccess to the target lesion. One such rapid exchange system utilizes a conventional inflation lumen and a relatively short guiding or through lumen at the distal end of the catheter to slidably receive the guide wire. The distal guide wire portion is permanently fused to the catheter body tube which is formed of a flexible material that allows the catheter to be pushed and advanced through curved vascular pathways.
Other "rapid exchange" catheter designs use a dedicated guide wire lumen provided with a longitudinal split seam. These designs enable the operating physician to remove the catheter by simply grasping the exposed proximal end of the implanted catheter and pulling the catheter tube off of the guide wire as it is removed while leaving the guide wire in place. Still other designs use a blade to split the catheter from the guide wire upon removal of the catheter from the patient. For example a sharpened blade may be mounted within the central bore of the catheter proximal Y-connector to slit the catheter and separate it from the guide wire as the catheter is extracted.
While these disposable catheter designs have proven effective under a variety of conditions, their disposability and specific functionality limit the capacity of the surgeon to adapt to changing or unexpected situations. This drives up the costs associated with their use as several alternative catheters may be necessary to accomplish a simple procedure. For example, it is often necessary to exchange entire catheters during angioplasty procedures. The catheter exchange may be required for any one of several reasons including catheter balloon malfunction, the inability of the specific balloon size to adequately dilate the vascular stenoses, or the need to insert an additional device to remove vascular material. In each of these situations, the original dilatation catheter must be removed and a new catheter inserted. It is estimated that about half of the angioplasty procedures require the use of more than one dilatation catheter. Presently, all of the catheters used during such procedures are discarded after a single use.
The disposal of these technically advanced, precision manufactured instruments which are otherwise suitable for repeat use reduces the efficiency of the entire procedure. Similarly, the use of two or more dilatation catheters in a single operation significantly increases the costs to both the patient and the medical provider as the patient must pay for the cost of an additional dilatation catheter which may be on the order of several hundreds of dollars. Further, due to the increased demand for alternative and replacement catheters, the medical provider must stock a larger inventory of catheters which requires more storage space and packaging. This also increases the amount of waste or recyclable matter associated with the use of multiple, non-reusable catheters during a single operation, further increasing the administrative burdens and associated expenses.
One early effort at overcoming the disadvantages associated with completely disposable catheters involved their resterilization and reuse. However, this proved to be unworkable in practice. Most of the currently available catheter designs are fabricated as substantially integral devices having the majority of components joined or fused together using permanent connections. Such configurations preclude the efficient resterilization of the apparatus. For example, many standard catheter designs incorporate a closed system inflation lumen that must be entirely purged prior to sterilization to ensure the effectiveness of the procedure. Complete purging of the system after use is labor intensive, time consuming and expensive, if possible at all. Moreover, in order to reuse the catheter several delicate pieces of the catheter assembly, including the fragile dilatation balloons, must be repeatedly subjected to harsh sterilization conditions which may increase the possibility of material deterioration and subsequent balloon malfunction.
An alternative solution to the problems associated with single use catheters may be found in copending U.S. patent application Ser. No. 08/265,602 which is directed to catheters incorporating separable components that may be reused or disposed of, as desired. Typically, these catheter designs incorporate a rugged, reusable proximal end portion combined with a disposable distal end portion fabricated from reliable, yet cost effective materials. The proximal ends of the catheters are designed to facilitate their cleaning and resterilization. As a result, components of these catheters may be resterilized and reused which results in substantially reduced costs. Although these reusable catheters are a significant improvement over prior art disposable catheters and allow for the economical use of alternative balloon sizes and configurations during surgery, precious surgical time may be required to change or replace the disposable distal ends. This substitution may be complicated further by the hectic environment of the operating room where the apparatus may be wet, slippery, and difficult to see or manipulate.
Accordingly, it is an object of the present invention to provide catheter designs which incorporate resterilizable and reusable components.
It is another object of the present invention to provide catheter designs having two operational ends that can be rapidly substituted for one another.
It is still another object of the present invention to provide dilatation catheters which allow for the uncomplicated substitution or modification of components and catheter configurations.
It is yet another object of the present invention to provide dilatation catheters which require less storage space than conventional catheters while simultaneously reducing the amount of packaging necessary to maintain their sterility prior to use.